Known in the art is a catalyst comprising an active magnesium halide and, carried thereon, a titanium compound for use in the production of an olefin polymer, including a homopolymer of ethylene or an .alpha.-olefin and a copolymer of ethylene and an .alpha.-olefin. In particular, such a known catalyst for olefin polymerization is, for example, comprised of a solid titanium catalyst component comprising magnesium, titanium, a halogen and an electron donor, and an organometallic compound catalyst component.
Various proposals have been made on the process for preparing the above-mentioned solid titanium catalyst component comprising magnesium, titanium, a halogen and an electron donor as essential components. It is also known in the art that a polymer having a high stereoregularity can be produced in high yield by polymerizing an .alpha.-olefin having at least three carbon atoms in the presence of the solid titanium catalyst component.
The conventional process for preparing the solid titanium catalyst component includes a process comprising contacting a hydrocarbon solution of a halogenated magnesium compound with a liquid titanium compound to form a solid product. It also includes a process comprising producing a hydrocarbon solution of halogenated magnesium and titanium compounds, followed by formation of a solid product in the presence of at least one electron donor selected from the group consisting of polycarboxylic acids, monocarboxylic esters, polycarboxylic esters, polyhydric compound esters, acid anhydrides, ketones, aliphatic ethers, aliphatic carbonates, alkoxylated alcohols, alcohols having an aryloxy group, organosilicon compounds having an Si--O--C bond and organophosphorus compounds having a P--O--C bond.
In this connection, it is known that the selection of a polycarboxylic acid (e.g., phthalic anhydride) as the electron donor leads to preparation of a solid titanium catalyst component with which an olefin (co)polymer having uniform particle size and less dust quantity can be obtained.
The present inventors have made investigations with a view toward developing a Ti catalyst for olefin polymerization with which an olefin (co)polymer having uniform particle size, less dust quantity and high bulk density can be produced. As a result, they have found that the (co)polymer having uniform particle size, less dust quantity and high bulk density can be produced by the use of a catalyst for olefin polymerization containing a solid titanium catalyst component which comprises, as essential components, (a) magnesium, (b) titanium, (c) a halogen, (d) a compound having at least two ether linkages existing through a plurality of atoms, (e) a hydrocarbon and (f) an electron donor other than the compound (d). Based on this finding, the present invention has been accomplished.